CN107577043B

CN107577043B - MEMS light modulator for display

Info

Publication number: CN107577043B
Application number: CN201610520637.2A
Authority: CN
Inventors: 爱德华·帕克奇亚恩
Original assignee: Ai DehuaPakeqiyaen
Current assignee: Ai DehuaPakeqiyaen
Priority date: 2016-07-04
Filing date: 2016-07-04
Publication date: 2021-10-08
Anticipated expiration: 2036-07-04
Also published as: CN107577043A

Abstract

The invention relates to a MEMS light modulator for a display. The electromechanical light modulator and backlight provide an efficient, low cost and high performance display. There is provided an electromechanical display element comprising: a shutter plate having a first end and a second end, supported on a surface using a plurality of standoffs attached at the first and second ends of the shutter plate, wherein a first force applied to the shutter plate moves the shutter plate in a plane substantially parallel to the surface in a transverse direction relative to the first force.

Description

MEMS light modulator for display

Related U.S. patent document

U.S. application No. 12/584,465, filed on 9/3/2009, is now U.S. patent No. 7,995,261B 2; U.S. application No. 14/589,699 filed on 5.1.2015; U.S. application No. 14/589,634 filed on 5.1.2015; U.S. application No. 14/589,434 filed on 5.1.2015; U.S. application No. 14/589,551 filed on 5.1.2015; U.S. application No. 14/589,715 filed on 5.1.2015, which is incorporated herein by reference.

Background

Technical Field

The present invention relates generally to displays. More particularly, the invention relates to displays comprising electromechanical picture elements.

Discussion of the related Art

Currently, liquid crystal displays occupy the major market for flat panel displays. Displays based on electromechanical light modulators are proposed as a viable alternative to LCDs. The present invention discloses electromechanical light modulators and displays that can compete with LCDs in terms of image performance, light efficiency, and cost.

Summary of The Invention

The following is a brief description of exemplary embodiments of the invention. It is provided as a prelude to the more detailed design discussion that follows that will be more quickly understood by those skilled in the art, and it is not intended in any way to limit the scope of the claims appended hereto in order to particularly point out the invention.

This specification discloses several electromechanical light modulators. According to an exemplary embodiment of the invention, the modulator includes one or two electrostatic actuators, a shutter plate supported over a surface of the substrate using a plurality of holders attached to the shutter plate at first and second ends of the shutter plate. In operation, the actuator applies a force to the shutter plate. The shutter plate holder limits movement of the shutter plate in the direction of the force and allows the shutter plate to move substantially in the direction transverse to the force. The shutter plate moves in a lateral direction between a first position and a second position without physical contact with a stationary part or surface. Each electrostatic actuator includes two electrodes positioned substantially parallel and in close proximity to each other. In some embodiments, the shutter plate is electrically conductive and acts as one of the actuator electrodes. In other designs, the shutter plate includes a flange extending at a right angle from an edge of the shutter plate and forms an electrostatic actuator with a fixed electrode. The fixed electrode may be positioned substantially close to the flange to form an effective electrostatic actuator.

The bezel supports are located between the bezels and the surface so that in the display the bezels may be positioned substantially close to each other, only allowing space for movement of the bezels between them. In some modulators, the mask is supported on a surface using a cantilever beam. Methods of manufacturing a cantilever beam and a visor supported by the cantilever beam are disclosed. The invention also discloses a display, comprising: a light absorbing layer having a light transmitting region, a backlight comprising a back reflector for reflecting light towards the light absorbing layer, and a plurality of modulators, each modulator comprising a gobo positioned between the backlight and the light absorbing layer, the gobo having a light transmitting region and a light reflecting surface facing the backlight for recycling light emitted from the backlight, wherein light impinging on the light transmitting region of the gobo from the backlight is transmitted through the light transmitting region of the light absorbing layer when the gobo is in a first position and is absorbed in the light absorbing layer when the gobo is in a second position.

The present invention also discloses another display, comprising: a plurality of modulators, each modulator comprising a mask having a light transmitting region; and a substrate having a surface and a plurality of embedded light reflectors, wherein the embedded light reflectors cause light to exit the substrate from the surface of the substrate and to converge at respective light transmitting regions of the bezel.

The foregoing and other objects of the invention are shown in the drawings and are described in the following specification.

Brief description of the drawings

Fig. 1A is a perspective view of a shutter assembly according to an illustrative embodiment of the present invention.

Fig. 1B is a front view of the shutter assembly shown in fig. 1A.

Fig. 2A is a top view of an exemplary mold for making the shutter assembly shown in fig. 1A.

Fig. 2B is a sectional view taken along line 2B in fig. 2A.

Fig. 3A is a perspective view of a light modulator according to an illustrative embodiment of the invention.

Fig. 3B is a front view of the light modulator shown in fig. 3A.

Fig. 3C is a front view of the light modulator shown in fig. 3A, showing the shutter plate in a first position.

Fig. 3D is a front view of the light modulator shown in fig. 3A, showing the shutter plate in a second position.

Fig. 4A is a perspective view of a light modulator according to an illustrative embodiment of the invention.

Fig. 4B is a front view of the light modulator shown in fig. 4A.

Fig. 5A is a perspective view of a light modulator according to an illustrative embodiment of the invention.

Fig. 5B is a front view of the light modulator shown in fig. 5A.

Fig. 6A is a perspective view of a light modulator according to an illustrative embodiment of the invention.

Fig. 6B is a side view of the light modulator shown in fig. 6A.

Fig. 6C is a perspective view showing a light shielding plate holder in the light modulator shown in fig. 6A.

Fig. 6D is a top view of the light modulator shown in fig. 6A.

Fig. 6E is a top view of the light modulator shown in fig. 6A, showing the shutter plate in a first position.

Fig. 6F is a top view of the light modulator shown in fig. 6A, showing the shutter plate at a second position.

Fig. 7A is a top view of a light modulator according to an illustrative embodiment of the invention.

Fig. 7B is a side view of the light modulator shown in fig. 7A.

Fig. 7C is a top view showing a mask holder in the light modulator shown in fig. 7A.

Fig. 7D is a top view of the light modulator shown in fig. 7A showing the shutter plate in a first position.

Fig. 8A is a perspective view of a visor holder according to an exemplary embodiment of the present invention.

Fig. 8B is a perspective view of a mold for manufacturing the light blocking plate holder shown in fig. 8A.

Fig. 8C is a sectional view taken along line C-C in fig. 8B, illustrating a step for manufacturing the light blocking plate holder shown in fig. 8A.

Fig. 8D is a top view showing a step for manufacturing the mask holder shown in fig. 8A.

Fig. 8E is a front view showing a step for manufacturing the mask holder shown in fig. 8A.

Fig. 8F is a front view showing a step for manufacturing the light shielding plate holder shown in fig. 8A.

Fig. 8G is a top view showing a step for manufacturing the light shielding plate holder shown in fig. 8A.

Fig. 8J is a side view showing a step for manufacturing the light shielding plate holder shown in fig. 8A.

Fig. 9A is a perspective view of a visor according to an exemplary embodiment of the present invention.

Fig. 9B is a perspective view of a mold for manufacturing the light shielding plate shown in fig. 9A.

Fig. 9C is a sectional view taken along line C-C in fig. 9B, illustrating a step for manufacturing the light shielding plate shown in fig. 9A.

Fig. 9D is a perspective view showing a step for manufacturing the light shielding plate shown in fig. 9A.

Fig. 9E is a sectional view taken along line E-E in fig. 9D, illustrating a step for manufacturing the light shielding plate shown in fig. 9A.

Fig. 9F is a sectional view taken along line F-F in fig. 9D, illustrating a step for manufacturing the light shielding plate shown in fig. 9A.

Fig. 10A is a perspective view of a display backlight according to an exemplary embodiment of the present invention.

Fig. 10B is a side view of the display backlight shown in fig. 10A.

Fig. 10C is an enlarged view of the area designated 10C in fig. 10B.

FIGS. 11A through 11D are cross-sectional views illustrating steps for fabricating an optical layer with an embedded light reflector, according to an illustrative embodiment of the invention.

Fig. 12A to 12C are sectional views showing steps for manufacturing a substrate with an embedded light reflector according to an exemplary embodiment of the present invention.

Fig. 13A is a plan view of a display cover assembly according to an exemplary embodiment of the present invention.

Fig. 13B is a sectional view taken along line 13B in fig. 13A.

Fig. 14A is a cross-sectional view of a display showing a light shield in a first position, according to an illustrative embodiment of the invention.

FIG. 14B is a cross-sectional view of the display shown in FIG. 14A, showing the bezel in a second position.

Fig. 15A is a cross-sectional view of a display showing a light shield in a first position, according to an illustrative embodiment of the present invention.

FIG. 15B is a cross-sectional view of the display shown in FIG. 15A, showing the bezel in a second position.

Description of the invention

FIG. 1A is a perspective view and FIG. 1B is a front view of a visor assembly 100 according to an illustrative embodiment of the present invention. The shutter plate assembly 100 includes a shutter plate 101 supported above a surface 103 of a transparent substrate 102 using support stands 104 and 105. The support 104 is attached at a first end 106 of the visor 101 and the support 105 is attached at a second end 107 of the visor 101. The

holders

104 and 105 are substantially straight and are inclined with respect to each other and with respect to the surface 103 and form an angle 113 with the surface 103 of between 70 and 85 degrees. The

holders

104 and 105 are attached to the surface 103 of the substrate 102 using pads 109 at a distance 114 that is greater than the distance 115 between the attachment points of the

holders

104 and 105 on the mask 101. The visor assembly 100 can be configured to have

holders

104 and 105 that are inclined relative to each other and attached to the surface 103 at a distance 114 that is less than the distance 115. The

holders

104 and 105 and the pads 109 are constructed of a thin conductive material and provide electrical connections from the surface 103 to the mask 101. The shutter plate 101 is also constructed of a thin conductive material or a multi-layer thin film including a conductive layer. The light barrier 101 includes a light transmitting zone 108 and a light blocking or blocking zone 110. The light blocking region 110 is larger (wider and longer) than the light transmitting region 108. Light-transmitting zone 108 transmits 90% or more of the light that strikes light-transmitting zone 108, while light-blocking zone 110 blocks at least 99% of the light.

The outer edge or all edges of the light blocking plate 101 are beveled to prevent the light blocking plate 101 from bending. The shutter plate 100 may be fabricated from a metal (e.g., aluminum and silicon alloys) on a mold. In one implementation, all surfaces of the mask 101 may have a light absorbing finish. In another implementation, the light shield 101 may have a light reflective first surface 120 and a light absorbing second surface 121. The light reflecting surface 120 reflects 80% or more of the light, and the light absorbing surface 121 absorbs 80% or more of the light.

Depositing a layer of aluminum on the smooth surface of the mold will provide the shadow mask 101 with a mirrored first surface 120, and a black oxide layer may be formed on the second surface 121 by anodic oxidation. The black oxide layer may be formed after etching the light-transmitting zone 108, so the inner edge of the light-transmitting zone 108 will be covered with the black oxide layer.

In addition, chromium oxide or niobium may be deposited or a black organic resin may be applied to the surface of the light shielding plate 101 to form a light absorbing surface.

Without limitation, portions of the visor assembly 100 may have the following dimensions. The shutter plate 101 may have a width 115 between 50 microns to 1000 microns and a thickness from 0.5 microns to 5 microns. Light-transmitting zone 108 may have a width 122 from 2 microns to 50 microns. The

holders

104 and 105 may have a width from 2 microns to 20 microns and a thickness from 0.5 microns to 5 microns.

Holders

104 and 105 may have a length 112 that is 1.5 to 3 times greater than width 122 of light-transmitting zone 108.

Fig. 2A and 2B illustrate a mold 200 for manufacturing the visor assembly 100. Fig. 2A is a top view of the mold 200, and fig. 2B is a cross-sectional view taken along line 2B in fig. 2A.

The mold 200 is fabricated on the surface 103 of the substrate 102 using gray scale or multi-mask photolithography. A layer of sacrificial material 201 is deposited on surface 103. A groove 203 and a recessed region 206 are formed on a surface 205 of layer 201. The shutter plate assembly 100 is constructed by depositing and selectively etching a thin layer of a conductive film on the surface of the mold 200. The

holders

104 and 105 are formed on the side walls 204 of the recess 203. The side wall 204 has the same inclination 113 as the

holders

104 and 105 with respect to the surface 103. The recessed region 206 is provided to configure the shutter plate 101 with beveled edges. The beveled edges help prevent the shutter plate 101 from bowing or bending. A combination of directional and conformal deposition of conductive material may be used to control the relative thicknesses of the

support shelves

104 and 105 and the shadow mask 101.

Fig. 3A through 3D show an optical modulator 300 according to an exemplary embodiment of the present invention.

Referring to fig. 3A and 3B, the modulator 300 includes the shutter plate assembly 100 of fig. 1A and a cover assembly 303. The lid assembly 303 includes a transparent substrate 304 supported over the surface 103 of the substrate 102 using

spacers

306 and 307. Two

electrodes

308 and 309 are formed on the inner surface 305 of the substrate 304.

The electrode 308 and the conductive light shield 101 form a first electrostatic actuator 311, while the electrode 309 and the conductive light shield 101 form a second electrostatic actuator 312. In operation, a voltage potential applied between the electrode 308 and the shutter plate 101 generates an electrostatic force (FIG. 3C) that pulls the holder 104 attached at the first end 106 of the shutter plate 101 to a nearly upright position relative to the surface 103 and moves the shutter plate 101 laterally (FIG. 3C) to a first position, or a voltage potential applied between the electrode 309 and the shutter plate 101 generates an electrostatic force (FIG. 3D) that pulls the holder 105 attached at the second end 107 of the shutter plate 101 to a nearly upright position relative to the surface 103 and moves the shutter plate 101 laterally (FIG. 3C) to a second position.

The stored mechanical force in the

holders

104 and 105 returns the shutter plate 101 from the first or second position to a mechanically resting or neutral position as shown in fig. 3B.

In the modulator 300, the first actuator 311 and the second actuator 312 each apply a force to the light shielding plate 101 in substantially the same direction and move the light shielding plate 101 laterally in opposite directions.

In fig. 3C, an arrow 314 indicates a direction of a force applied to the light shielding plate 101 by the first actuator 311, and an arrow 315 indicates a direction of lateral movement of the light shielding plate 101 from the mechanical rest position to the first position. The lateral movement of the light-shielding plate 101 from the mechanical rest position to the first position is at least five times more (at five times) than in the direction of the force applied to the light-shielding plate 101 by the first actuator 311.

In fig. 3D, arrow 316 indicates the direction of the force applied to the light blocking plate 101 by the second actuator 312, while arrow 317 indicates the direction of the lateral movement to the second position by the light blocking plate 101.

Applying an increasing voltage to the actuator 311 and a decreasing voltage to the actuator 312 will gradually move the shutter plate between the first position and the second position, or applying a fixed voltage to the actuator 311 and a variable voltage to the actuator 312 will also gradually move the shutter plate between the first position and the second position.

In a display, the

electrodes

308 and 309 may be formed wider and shared by the shutter plate assemblies in successive rows or columns.

Fig. 4A and 4B show an optical modulator 400 according to an illustrative embodiment of the invention. The modulator 400 includes a shutter plate assembly 401 and a cover assembly 418. The shutter plate assembly 401 includes a shutter plate 410 supported above a surface 403 of a transparent substrate 402 using support stands 406 and 407. The support frame 407 is attached at a first end 408 of the visor 410 and the support frame 406 is attached at a second end 409 of the visor 410. The light blocking plate 410 is formed of an electrical insulator or dielectric material and includes a light transmitting region 411 and a light blocking region 412. The mask 410 further includes a first electrode 405 and a second electrode 404. Holder 407 provides an electrical connection from surface 403 to electrode 405, while holder 406 provides an electrical connection from surface 403 to electrode 404.

The cover assembly 418 includes a transparent substrate 413 supported on the surface 403 using

spacers

416 and 417. The lid assembly 418 also includes a transparent conductive layer 415 formed of a material such as thin indium oxide on the inner surface 414 of the substrate 413.

In the modulator 400, a first electrode 405 with a conductive layer 415 forms a first electrostatic actuator 418, and a second electrode 404 with a conductive layer 415 forms a second electrostatic actuator 419.

In operation, the first actuator pulls the holder 407 to a nearly upright position relative to the surface 403 and moves the mask 410 laterally to a first position, while the second actuator pulls the holder 406 to a nearly upright position relative to the surface 403 and moves the mask 410 laterally to a second position. The stored mechanical force in the

holders

406 and 407 returns the shutter plate 410 from the first or second position to a mechanical rest or neutral position, as shown in fig. 4B.

Fig. 5A and 5B show an optical modulator 500 according to an illustrative embodiment of the invention. The modulator 500 includes

spacers

508 and 509 and a shutter plate assembly 503 formed of a polymer on a surface 502 of a substrate 501. The shutter plate assembly 503 includes a shutter plate 507 and shutter

plate holders

505 and 506 formed of a conductive material and attached to

bulkheads

508 and 509 using

conductive pads

512 and 513.

The modulator 500 also includes two

electrodes

510 and 511 formed on the surface 502 of the substrate 501. The electrode 510 and the conductive shadow 507 form a first electrostatic actuator 514, while the electrode 511 and the conductive shadow 507 form a second electrostatic actuator 515.

The shutter plate assembly 503 may be constructed similarly to the shutter plate assembly 401, and the two

electrodes

510 and 511 may be replaced with a transparent conductive layer.

Fig. 6A through 6F show an optical modulator 600 according to an illustrative embodiment of the invention. Referring to fig. 6A through 6C, a modulator 600 includes a mask 601 constructed of a conductive material and includes a light transmitting region 602 and a light blocking region 603.

The mask is supported on the surface 605 of the substrate 604 using four

cantilever beams

606 and 607 formed between the mask 601 and the surface 605 and substantially within the boundaries of the mask 601 (fig. 6C). A first end of each

cantilevered beam

606 and 607 is attached to the surface 605 using a post 609 and a conductive pad 610, while a second end is attached to the bezel 601 using a post 608. The cantilevered beam 606 is attached at a first end 618 of the bezel 601 and the cantilevered beam 607 is attached at a second end 617 of the bezel 601.

Beams

606 and 607 are positioned substantially parallel to surface 605 and spaced apart from surface 605 by a first gap 619. The

beams

606 and 607 are also positioned substantially parallel to the shutter plate 601 and spaced apart from the shutter plate 601 by a second gap 620. The cantilever beams 606 and 607 may be formed to be thin and long so that they may bend or flex without requiring substantial force. Further, the

beams

606 and 607 may be formed with sufficient height to be oriented perpendicular to the surface 605 to support the weight of the shutter plate 601.

The shield 601 also includes a first flange 613 extending from a first end or edge 618 of the shield 601 toward the surface 605 within 5 degrees from normal to the surface 605. The bezel 601 also includes a second flange 615 extending from a second edge 617 towards the surface 605 within 5 degrees from normal to the surface 605.

Beams

606 and 607 are inclined relative to a surface 629 of flange 613 and form an angle 628 (fig. 6D) of between 70 and 89 degrees.

The modulator 600 also includes two

electrodes

614 and 616 that extend from the surface 605 at approximately a right angle. Electrode 614 is attached to surface 605 using conductive pad 611, while electrode 616 is attached to surface 605 using conductive pad 612. The electrode 614 and the flange 613 form a first electrostatic actuator 622, while the electrode 616 and the flange 615 form a second electrostatic actuator 621.

In operation, the actuator 622 applies a first force 625 to the shutter plate 601, pulling the beam 606 attached at the first end 618 of the shutter plate 601 and moving the shutter plate 601 to a first position substantially in a lateral direction 626 relative to the first force 625 (fig. 6E), while the actuator 621 applies a second force 627 to the shutter plate 601, pulling the beam 607 attached at the second end 617 of the shutter plate 601 and moving the shutter plate 601 to a second position substantially in a lateral direction 628 relative to the second force 627 (fig. 6F). The shutter plate 601 moves at least 5times more in the lateral direction 626 than in the direction of the first force 625 (at least 5 times).

The stored mechanical force in

beams

606 and 607 returns the shutter plate 601 from the first or second position to a mechanically resting or neutral position as shown in fig. 6D. The shutter plate 601 moves between a first position and a second position in a plane substantially parallel to the surface 605.

As the shutter plate 601 moves from the mechanical rest position (fig. 6D) to the first position (fig. 6E), the linear distance between the

posts

608 and 609 attached to the ends of the beam 607 increases. For this reason, beam 607 is formed to bend slightly to compensate for the increased linear distance between

posts

608 and 609.

Fig. 7A to 7D show an optical modulator 700 according to an exemplary embodiment of the present invention. The modulator 700 includes a mask 701 constructed of a conductive material and includes a light transmitting region 702 and a light blocking region 703. The shutter plate 701 also includes a first flange 708 attached to the shutter plate 701 at the first end 706. The shutter plate 701 is supported on a surface 704 of the base 705 using four cantilever beams 712 and 714 (fig. 7C).

A first end of each

cantilevered beam

712 and 714 is attached to the surface 704 using a post 716 and a conductive pad 717, while a second end is attached to the bezel 701 using a post 715. The cantilevered beam 714 is attached at the first end 706 of the shutter plate 701 and the cantilevered beam 712 is attached at the second end 707 of the shutter plate 701. The cantilevered beams 712 and 714 are substantially straight. The cantilevered beam 714 is inclined relative to the flange 708 and forms an angle 717 between 70 and 89 degrees, while the cantilevered beam 712 forms an angle 731 with the flange 708 that is approximately 90 degrees.

Modulator 700 also includes an electrode 709 extending perpendicularly from surface 704 and attached to surface 704 using conductive pad 710. The electrode 709 and the flange 708 of the shutter plate 701 form an electrostatic actuator 711.

In operation, the actuator 711 pulls the beam 714 attached at the first end 706 of the shutter plate 701 in a direction 720 and moves the shutter plate 701 to a first position substantially in a lateral direction 721 relative to the direction 720 (fig. 7D). The stored mechanical force in the

beams

712 and 714 returns the shutter plate 701 from the first position to a mechanically resting or neutral position (fig. 7A). The shutter plate 701 moves between positions in a plane substantially parallel to the surface 704.

The modulator 700 may also include a second electrostatic actuator 725 formed by a second flange 722 attached to the shutter plate 701 at the second end 707 and a second electrode 723 extending perpendicularly from the surface 704 and attached to the surface 704 using a conductive pad 724. In the modulator 700, the support frame 712 constrains the shutter plate 701 and the second flange 722 to move closer to the second electrode 723 so that the second electrode 723 can be located at a close distance from the second flange 722 to form an effective actuator.

In a display, a pixel processing voltage may be applied to the second actuator 725 for selectively holding the shutter plate 701 at a mechanically neutral position.

Fig. 8A through 8F show the manufacturing steps of the mask holder 800 according to an exemplary embodiment of the present invention, similar to those in the

modulators

600 and 700. FIG. 8A shows a mask support 800 including a cantilever beam 803. A first end of beam 803 is attached to a first post 804 that connects beam 803 to surface 801 of substrate 802 using a solder pad 805, while a second end of beam 803 is attached to a second post 806 that is later connected to the shadow mask. The first post 804 and the second post 806 each have three sides and a top.

Holder 800 is formed on mold 807. The first fabrication step is to form a mold 807 from a sacrificial material on surface 801 of substrate 802 (fig. 8B). Mold 807 is formed in the shape of a rectangular prism and has four

sidewalls

808, 809, 810, and 811 and a top 812. The sidewalls are oriented perpendicular to surface 801 within +/-5 degrees from normal. The next steps are to deposit a conformal layer of conductive material 814 by magnetron sputtering on the surface of mold 807 and surface 801 and to apply a conformal layer of positive photoresist 815 over conductive layer 814 by electrophoretic deposition or spray coating (fig. 8C).

The next step is to position a first photomask 816 on mold 807 (fig. 8D) and illuminate photoresist layer 815 from the direction of

sidewalls

808 and 809 with a UV light source of collimated and tilted rays having a divergence of less than 2 degrees and a tilt angle 817 between 45 and 75 degrees relative to surface 801 (fig. 8E and 8F). Mold 807 and first photomask 816 block UV light from the areas on photoresist layer 815 that are defined in the geometry of cantilever beams 803, first posts 804, second posts 806, and pads 805. Another step is to position a second photomask 818 over mold 807 (fig. 8G) and to illuminate photoresist layer 815 from the direction of sidewalls 811 (fig. 8J). This will illuminate the photoresist layer 815 applied on the lower portion of the sidewall 811. If the second terminals 806 are formed with only two sides formed on the

sidewalls

808 and 809 and the top of the mold 807, the steps shown in fig. 8G and 8J may be omitted.

After illumination from all three directions, photoresist layer 815 is developed and the unprotected areas of conductive layer 814 are removed by etching. Cantilevered beam 803 formed on mold 807 has a width equal to the thickness of conductive layer 814.

Where conductive layer 814 is formed of a material that reflects UV light, such as aluminum, a light absorbing layer may be applied or formed over conductive layer 814 prior to applying photoresist layer 815. This will reduce the reflection of UV light from horizontal and vertical surfaces. To reduce reflections from the surface of photoresist layer 815, the mold and mask may be immersed in a liquid having a similar refractive index as photoresist layer 815.

Fig. 9A through 9F show fabrication steps of a mask 900 and an electrode 905 according to an exemplary embodiment of the present invention, similar to

modulators

600 and 700.

Fig. 9A shows a light blocking plate 900 including a light transmitting region 901 and a flange 902. The shutter plate 900 is attached to the posts 806 of the cradle 800 described above. Fig. 9A also shows electrodes 905 attached to surface 801 of substrate 802 using pads 904.

The first fabrication step forms a mold 910 (fig. 9B) comprising two

rectangular prisms

911 and 912 from a sacrificial material on surface 801 of substrate 802. Prism 911 includes four

sidewalls

914, 915, 916, 917 and a top 918. The prism 912 includes four

sidewalls

920, 921, 923, 924 and a top 925. The sidewalls are oriented perpendicularly relative to surface 801 within +/-5 degrees from normal. A through hole 926 is formed in the top 918 of the prism 911 for connecting the shutter plate 900 to the terminal 806 of the support stand 800.

The next steps are to deposit a conformal layer of conductive material 930 on the surface of mold 910 and surface 801 and a conformal layer of negative photoresist 931 on conductive layer 930 (fig. 9C).

The next step is to position photomask 932 over mold 900 (fig. 9D) and illuminate photoresist layer 931 from the direction of

sidewalls

916 and 924 with a UV light source having collimated and oblique rays (fig. 9E and 9F).

Mask 932 blocks UV light illumination of photoresist layer 931 applied over the surfaces of

sidewalls

915, 916, 917, 920, and 923 and over an area of top surface 918 over which light transmission regions 901 of light shield 900 are formed. The mold blocks a lower portion of the surface of

sidewalls

914 and 921, on which flange 902 and electrode 905 are formed, and a portion of surface 801 between

sidewalls

914 and 921.

After illumination from both directions, the photoresist layer 931 is developed and the unprotected areas of the conductive layer 930 are etched.

The next step is to remove the sacrificial layer and release the shutter plate 900 and the support stand 800.

The shutter plate 900 may be formed to include flanges, such as flanges 902 on all four edges of the shutter plate 900. These flanges effectively block stray light from leaving the display, thereby improving contrast.

Fig. 10A, 10B, and 10C show a display backlight 1000 according to an exemplary embodiment of the present invention. Fig. 10A is a perspective view of the backlight 1000, fig. 10B is a side view of the backlight 1000, and fig. 10C is an enlarged view of the region designated as 10C in fig. 10B.

The backlight 1000 includes a generally planar optical waveguide 1001 constructed of acrylic or other transparent material having a refractive index n1 with a value between 1.45 and 1.6. Optical waveguide 1001 includes a top surface 1002, a bottom surface 1003, opposing

side surfaces

1004 and 1005, and a light input end 1006. The bottom surface 1003 is inclined relative to the top surface 1002 and forms an angle 1009 (fig. 10B) having a value between about 0.1 and 2.0 degrees. The bottom surface 1003 converges with the top surface 1002 in a direction away from the light input end 1006.

The backlight 1000 also includes a light absorbing film 1010 located proximate the bottom surface 1003 of the light guide 1001 and a plurality of light sources 1011 located proximate the light input end 1006.

Backlight 1000 also includes a first light layer 1015 constructed of a substantially transparent material having an index of refraction n2 with a value between about 1.45 and 1.6. First light layer 1015 includes a light exit surface 1016, a light input surface 1017, and a plurality of embedded light reflectors 1018 positioned between light input surface 1017 and light exit surface 1016. The light reflector 1018 is formed of a thin light reflective material, such as aluminum or silver. The light reflector 1018 may have a substantially flat surface or a curved surface having a cross-section with a radius of curvature of about 20-80 microns. The light reflector 1018 is inclined with respect to the top surface 1002 of the light guide 1001 and forms an angle 1026 having a value between approximately 20 degrees and 40 degrees.

The backlight 1000 also includes a second light layer 1020 formed between the light input surface 1017 of the first light layer 1015 and the top surface 1002 of the light guide 1001. Second optical layer 1020 is constructed from a fluoropolymer or other substantially transparent material having an index of refraction n3 with values of approximately 1.3 and 1.4.

In operation, a light ray 1023 entering from the light input end 1006 of the optical waveguide 1001 is reflected from the top and

bottom surfaces

1002, 1003 and changes angle towards a normal relative to the top surface 1002. When the angle of incidence to the top surface 1002 is less than the critical angle 1024 (FIG. 10C) defined by the refractive index n1 of the optical waveguide 1001 and the refractive index n3 of the second optical layer 1020, the light ray 1023 exits the optical waveguide 1001. Light ray 1023, which passes through second optical layer 1020, enters first optical layer 1015 from light input surface 1017 and changes the angle defined by refractive index n2 of first optical layer 1015. A majority of light rays 1023 that enter first light layer 1015 are internally reflected from light exit surface 1016. Light rays exit the first light layer 1015 from the light exit surface 1016 by reflecting from the embedded light reflector 1018. Light rays reflected from curved light reflector 1018 exit first light layer 1015 from light exit surface 1016 and converge at a distance 1025 from light exit surface 1016.

The backlight 1000 can also include a transparent substrate, such as a glass substrate, and a dichroic filter layer interposed between the first light layer 1015 and the second light layer 1020.

Steps for fabricating the optical layer 1108 with an embedded optical reflector or optical reflective facet 1106 are shown in fig. 11A through 11D. In step (a), a microprism 1101 is fabricated on a substrate 1103 from a transparent UV curable liquid polymer using photolithography. In step (B), the base 1103 is tilted about an angle 1105 (fig. 11B), and the extensions 1104 of the microprisms 1101 are formed from the same liquid polymer. Microprisms 1101 having extensions 1104 may also be molded. In step (C), a mirror film is deposited on each facet of the extension 1104 to form a light reflecting facet 1106. In step (D), the recesses 1107 are filled with the same UV-curable liquid polymer. FIG. 11D shows the complete construction of optical layer 1108 with embedded light-reflecting facet 106.

The optical layer 1108 may be combined with the

shutter plate assembly

100 or 401 in the

modulators

300 and 400 disclosed above. The optical layer 1108 may be constructed on the substrate and between the reticle supports prior to construction of the

reticle assembly

100 or 401. For

modulators

500, 600, or 700 having a shutter plate located at a close distance from the surface of the substrate, an embedded light reflector may be constructed in the substrate.

Fig. 12A, 12B, and 12C show steps of fabricating a glass substrate 1200 with an embedded light reflector 1205 according to an illustrative embodiment of the invention. The first step is to etch the grooves 1203 in the glass substrate 1200. The next three steps are similar to steps B, C and D described above. The second step is to tilt the substrate 1200 and form an extension 1204 of UV cured liquid polymer inside each recess. The third step is to deposit a mirror film on the extended portion 1204 to form the light reflecting facets 1205. The fourth step is to fill the grooves with the same UV curable liquid polymer. Fig. 12C shows a glass substrate 1200 constructed with an embedded light reflector 1205. The cured polymer preferably has substantially the same refractive index as the glass substrate 1200. In the backlight 1000, the first light layer 1015 may be replaced with a glass substrate 1200, and the

modulator

500, 600, or 700 may be configured on the glass substrate 1200.

Fig. 13A and 13B show a display cover assembly 1400 according to an illustrative embodiment of the present invention. The cover assembly 1400 includes a transparent substrate 1401 having a first surface 1402 and a second surface 1403. The cap assembly 1400 further includes a light diffusion layer 1404 formed on the first surface 1402 and a light absorbing layer 1405 formed on the light diffusion layer 1404. For thin substrates having a thickness of 200 microns or less, a diffusion layer 1404 may be formed on the second or outer surface 1403 and a light absorbing layer 1405 may be formed on the inner surface 1402 of the substrate 1401. The light absorbing layer 1405 includes light transmitting regions 1407 and opaque light absorbing regions 1406. The lid assembly 1400 may also include electrodes, such as

electrodes

308 and 309 of the modulator 300 formed on the opaque light absorbing regions 1406 of the light absorbing layer 1405 having a light reflecting mirror surface or electrode 415 in a transparent conductive layer (such as in the modulator 400).

The light absorbing layer 1405 may be formed of a conductive material. The conductive light absorbing layer 1405 may act as an electrode for an EMI or electrostatic shield in a display or an actuator, such as an actuator in the modulator 400.

The light absorbing layer 1405 can absorb 80% or more of the light incident on the opaque light absorbing regions 1406 and transmit less than 1% of the light.

Displays based on electromechanical light modulators may include a large number of modulators arranged in rows and columns. Each picture element or pixel in the display may comprise one or more modulators. For illustrative purposes, the following figures show a display with only one modulator.

Fig. 14A and 14B show cross-sectional views of a display 1500 according to an illustrative embodiment of the invention. The display 1500 includes a cover assembly 1501, a modulator 1502, and a backlight 1503 including a rear reflector 1504. The cap assembly 1501 includes a transparent substrate 1505, a light diffuser layer 1506 formed on a first surface 1507 of the substrate 1505, and a light absorbing layer 1508 formed on the light diffuser layer 1506. The light absorbing layer 1508 includes a light transmitting region 1509 and an opaque light absorbing region 1510. The modulator 1502 includes a mask 1511 having a light transmitting region 1514 and a light blocking region 1515. A surface facing the light shielding plate 1511 of the backlight 1503 is a light reflecting surface, and a surface facing the light absorbing layer 1508 is a light absorbing surface. The light transmitting region 1509 of the light absorbing layer 1508 is larger than the light transmitting region 1514 of the light blocking plate 1511 and smaller than the light blocking region 1515 of the light blocking plate 1511. The light shielding plate 1511 is in the first position or on position in fig. 14A, and the light shielding plate 1511 is in the second position or off position in fig. 14B. Light 1520 striking the light-transmitting region 1514 of the baffle 1511 from the backlight 1503 is transmitted through the light-transmitting region 1509 of the light absorbing layer 1508 when the baffle 1511 is in the first position (fig. 14A) and absorbed in the light absorbing layer 1508 when the baffle is in the second position (fig. 14B). Light impinging on the light blocking regions 1515 of the bezel 1511 reflects back to the backlight 1503 and is recycled by reflecting from the rear reflector 1504. The modulator 1502 may be any one of the modulators disclosed above or a modulator including a light shielding plate having a light reflecting surface facing the backlight 1503 for recycling light emitted from the backlight 1503.

It is important to design a modulator where the mask holder does not occupy substantially more of the display surface than the mask would need to, so that the masks can be positioned substantially close to each other, allowing only motion of the masks and space for some conductors between them.

The visor assembly disclosed above meets this need. In contrast to some prior art shutter assemblies in which the shutter support is located at the side of the shutter and occupies more than 50% of the display surface, in the shutter assembly disclosed above, the shutter support is located between the shutter and the surface over which the shutter is supported and substantially within the boundaries of the shutter that include movement of the shutter between the first and second positions.

This increases the light efficiency and reduces the gap between the rows and columns of the display by increasing the total light transmission area relative to the display surface.

In the display 1500, the light absorbing layer 1508 may be formed of a conductive material and may replace the electrodes 415 in the modulator 400 disclosed above.

The

electrodes

308 and 309 of the modulator 300 may be formed on the light absorbing layer 1508 having a light reflecting surface facing the backlight 1503, and the shutter plate 101 may be supported on a surface 1522 of the substrate 1521. The mask 601 of the modulator 600 and the mask 701 of the modulator 700 may also be supported on a surface 1522 of a substrate 1521. The

baffles

508 and 509 of the modulator 500 may be formed on the light absorbing layer 1508 and the baffle 503 may be suspended by the

baffles

508 and 509.

In display 1500, backlight 1503 emits surface light and may be an edge-lit or directly-lit backlight known from LCD displays.

Fig. 15A and 15B show cross-sectional views of a display 1700 according to an illustrative embodiment of the invention. The display 1700 includes a cover assembly 1701, a modulator 1702, and a backlight 1703. The cover assembly 1701 includes a transparent substrate 1705, a light diffuser layer 1706 formed on a first surface 1707 of the substrate 1705, and a light absorbing layer 1708 formed on the light diffuser layer 1706. Light absorbing layer 1708 includes light transmitting region 1709 and light absorbing region 1710. Modulator 1702 includes a mask 1711 having a light transmitting region 1714 and a light blocking region 1715. The surface of the mask 1711 facing the backlight 1703 may be a light reflecting surface or a light absorbing surface, and the surface facing the light absorbing layer 1708 is a light absorbing surface. The light transmission region 1709 of the light absorbing layer 1708 is larger than the light transmission region 1714 of the light blocking plate 1711 and smaller than the light blocking region 1715 of the light blocking plate 1711. Modulator 1702 also includes a substrate 1716 having a light exit surface 1721 and embedded light reflecting facets 1717. The facets 1717 are curved and cause light 1720 from the backlight 1703 to exit the substrate 1716 and to converge at the light transmitting regions 1714 of the bezel 1711. The shutter plate 1711 is supported on a surface 1721 of the base 1716. The backlight 1703 includes a light guide 1719 and a light layer 1718 positioned between the light guide 1719 and a substrate 1716. The backlight 1703 is similar to the backlight 1000 of fig. 10A to 10C. The backlight 1703 also includes a light absorbing layer 1704 behind the light guide 1719 for absorbing stray light or light reflected from the mask 1711.

The shutter plate 1711 is at a first position or on position in fig. 15A, and the shutter plate 1711 is at a second position or off position in fig. 15B. The light 1720 emitted from the substrate 1716 is transmitted through the light transmission region 1714 of the mask 1711 and the light transmission region 1709 of the light absorption layer 1708 when the mask 1711 is in the first position (fig. 15A), and is blocked by the light blocking region 1715 of the mask 1711 when the mask 1711 is in the second position (fig. 15B). Light reflected back from the light blocking region 1715 of the mask 1711 is absorbed in the light absorbing layer 1704.

In display 1700, the curved reflector 1717 increases the viewing angle of the display and reduces the required distance of movement of the bezel 1711 between the on position and the off position compared to a planar reflector.

The displays described above may also include spacers for maintaining a precise distance between the substrates, row and column conductors formed on one or both substrates, one or more thin film transistors and storage capacitors for handling the display pixels, a ground or power plane, a common interconnect for resetting the display pixels, dichroic filters or color filters, and an anti-reflective coating.

The displays described above may be labeled as electromechanical, micromechanical, microelectromechanical, or microelectromechanical systems (MEMS) displays. The display described above may be a monochrome display, a colour display or a colour sequential display.

Having now described the invention in detail as required by the patent statutes, those skilled in the art will appreciate that there are no difficulties in making changes and modifications to the various parts or their related components or methods of manufacture in order to meet the particular requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the present invention as set forth in the following claims.

Claims

1. An electromechanical display element comprising:

a visor having opposing first and second ends, the visor supported on a surface of a substrate using a plurality of standoffs attached at the first end of the visor and a plurality of standoffs attached at the second end of the visor, the standoffs located between the visor and the surface of the substrate and a longitudinal direction of the standoffs positioned substantially parallel to the surface of the substrate, the visor further comprising a first flange extending from the first end of the visor and forming a first electrostatic actuator with a first fixed electrode, wherein the first electrostatic actuator applies a force to the first flange and pulls each of the standoffs attached at the first end of the visor from an oblique position relative to the surface of the first flange to an almost normal position relative to the surface of the first flange, and moving the shutter plate from a mechanically neutral position to a first position in a lateral direction relative to the applied force, the cradle attached at the first end of the shutter plate restricting movement of the shutter plate in the direction of the force applied by the first electrostatic actuator and preventing physical contact between the first flange and the first fixed electrode.

2. An electromechanical display element comprising:

a shutter plate having opposing first and second ends, the shutter plate supported on a surface of a substrate using a plurality of standoffs attached at the first end of the shutter plate and a plurality of standoffs attached at the second end of the shutter plate, the standoffs located between the shutter plate and the surface of the substrate and a longitudinal direction of the standoffs positioned substantially parallel to the surface of the substrate, the shutter plate further comprising a first flange extending from the first end of the shutter plate and forming a first electrostatic actuator with a first fixed electrode and a second flange extending from the second end of the shutter plate and forming a second electrostatic actuator with a second fixed electrode, wherein the first electrostatic actuator applies a first force to the first flange and each of the standoffs attached at the first end of the shutter plate is supported from opposite the first end and a second end A tilted position of a surface of a flange is pulled to an almost normal position with respect to a surface of the first flange and the shutter plate is moved to a first position in a lateral direction with respect to an applied first force, the second electrostatic actuator applies a second force to the second flange and pulls each of the holders attached at the second end of the shutter plate from the tilted position with respect to the surface of the second flange to an almost normal position with respect to the surface of the second flange and moves the shutter plate to a second position in the lateral direction with respect to the applied second force, the holder attached at the first end of the shutter plate restricts movement of the shutter plate in a direction of the force applied by the first electrostatic actuator and prevents physical contact between the first flange and the first fixed electrode, the support bracket attached at the second end of the shutter plate limits movement of the shutter plate in the direction of the force applied by the second electrostatic actuator and prevents physical contact between the second flange and the second fixed electrode.

3. An electromechanical display element according to claim 1 or 2, wherein the light shield is supported on the surface of the substrate using cantilever beams, and wherein a first end of each of the cantilever beams is attached to the surface of the substrate using a first stud and a second end is attached to the light shield using a second stud.

4. An electromechanical display element according to claim 1, wherein the shutter plate further comprises a second flange extending from the second end of the shutter plate and forming a second electrostatic actuator with a second fixed electrode, the longitudinal direction of the holders being substantially straight, and the holders attached at the first end being inclined with respect to the holders attached at the second end, the longitudinal direction of each holder attached at the second end of the shutter plate being positioned almost normal with respect to the surface of the second flange.

5. An electromechanical display element according to claim 2, wherein a longitudinal direction of the holder attached at the first end is substantially straight and a longitudinal direction of the holder attached at the second end is curved.

6. An electromechanical display element according to claim 1 or 2 wherein the stand is located between the shutter plate and the surface and substantially within the boundaries of the shutter plate, and the stand is spaced from the shutter plate by a first gap and from the surface of the substrate by a second gap.

7. An electromechanical display element according to claim 1 or 2, wherein a longitudinal direction of the holder attached at the first end of the shutter plate forms an angle between 70 degrees and 89 degrees with respect to a surface of the first flange.

8. An electromechanical display element according to claim 1 or 2, wherein each said flange extends within 5 degrees from normal with respect to the surface of the substrate.

9. An electromechanical display element according to claim 1 or 2, wherein the light shield comprises a light absorbing first surface and a light reflecting second surface.

10. An electromechanical display element according to claim 1 or 2, wherein the first electrostatic actuator applies a first force to the shutter plate and moves the shutter plate at least 5times more in a lateral direction relative to the first force than in a direction of the first force.

11. An electromechanical display element according to claim 1 or 2, wherein the shutter plate moves between the first position and the second position in a plane substantially parallel to a surface of the substrate.